The present invention relates to a color image forming device having an intermediate image transfer member and a plurality of electrostatic latent image bearing bodies disposed following the movement direction of the intermediate image transfer member. Each of the electrostatic latent image bearing bodies is for developing a different color of an image,
A tandem type color image forming device has been known in which toners of cyan, magenta, yellow and black are contained in respective developing units, and electrostatic latent image bearing bodies each disposed beside each developing unit are aligned in a direction. According to the tandem type device, developing operations in the respective developing units are performed almost concurrently. Therefore, color image can be formed at high speed.
However, in the conventional tandem type color image forming device, a plurality of process units each including a photosensitive drum and a developing device are arrayed linearly in a direction parallel with an installing floor for the image forming device. Consequently, large installation area is required.
To avoid this problem, Japanese Patent Application publication No. Hei-8-190245 discloses a color image forming device in which the plurality of the process units are arrayed in a vertical direction to reduce the installation area of the entire device. However, in the disclosed color image forming device, a sheet discharge tray projects from a side wall of the image forming device, and each developing device is bulky and has a complicated construction. Consequently, resultant image forming device becomes bulky.
Further, in the conventional device, a vertical side wall plate is pivotably supported to a main frame, so that the side wall plate can be opened and closed for exchanging the process unit with a new unit. The vertical side wall plate extends in a direction perpendicular to each rotation axis of each photosensitive drum. That is, the side wall plate is positioned in confrontation with each end of each photosensitive drum. At this place, there is provided a mechanism for positioning the rotation shaft of the photosensitive drum, or a mechanism for positioning a rotation shaft of a drive roller for driving the intermediate image transfer belt. These mechanisms will become obstacles against the exchanging work, and will degrade the accurate positioning of the exchanged process unit. As a result, color image displacement may occur in the resultant color image in which one color image is slightly displaced from the other color images.
It is an object of the present invention to provide a compact color image forming device capable of being installed in a limited installation area.
Another object of the present invention is to provide such device eliminating displacement of one color image from other color images in a image recoding sheet.
These and other objects of the present invention will be attained by an improved color image forming device including a frame, an elongated intermediate image transfer member, a plurality of electrostatic latent image bearing bodies, a plurality of chargers, a plurality of exposure units, a plurality of developing units. The frame includes a pair of side frames. The elongated intermediate image transfer member runs substantially in a vertical direction and is positioned between the pair of side frames. The intermediate image transfer member has a first side. The plurality of electrostatic latent image bearing bodies are aligned substantially in the vertical direction and are positioned in confrontation with the first side of the intermediate image transfer member. Each electrostatic latent image bearing body has a latent image bearing surface. The plurality of chargers charge the latent image bearing surface of corresponding ones of the electrostatic latent image bearing bodies The plurality of exposure units expose charged surfaces of corresponding ones of the electrostatic latent image bearing bodies. The plurality of developing units each includes a developing agent bearing body disposed in confrontation with a corresponding one of the plurality of electrostatic latent image bearing bodies and houses therein developing agents of different colors. At least each developing unit is assembled in each process cartridge, and each process cartridge is detachably positioned at a side facing the first side and is moved in an attachment/detachment direction toward and away from the first side for attachment and detachment of the process cartridge with respect to the pair of side frames.
In another aspect of the invention, there is provided a color image forming device including the frame, the plurality of electrostatic latent image bearing bodies, an elongated intermediate image transfer member, a plurality of developing units, a plurality of chargers, and the plurality of exposure units. The elongated intermediate image transfer member runs substantially in a vertical direction and has a first side running downwardly. The plurality of developing units each includes the developing agent bearing body and a layer thickness regulation member in contact with the developing agent bearing body and positioned below the developing agent bearing body for regulating a thickness or a layer of the developing agent formed thereon. The developing agent comprises a non-magnetic single component type developing agent. The plurality of chargers is each positioned in confrontation with the latent image bearing surface of corresponding ones of the electrostatic latent image bearing bodies for charging the latent image bearing surface.
In still another aspect of the invention, there is provided a color image forming device including a frame, an elongated intermediate image transfer member, a plurality of electrostatic latent image bearing bodies, a plurality of developing units, a supply tray and a discharge tray. The elongated intermediate image transfer member runs substantially in a vertical direction, and has a first side running downwardly. The plurality of electrostatic latent image bearing bodies are aligned substantially in the vertical direction and are positioned in confrontation with the first side of the intermediate image transfer member. Each electrostatic latent image bearing body has a latent image bearing surface. The plurality of developing units each includes the developing agent bearing body. The supply tray is adapted for supplying an image recording medium to the intermediate image transfer member. The discharge tray is adapted for receiving an image recording medium formed with a color image. The intermediate image transfer member, the plurality of the electrostatic latent image bearing bodies, and the plurality of the developing units are positioned below the discharge tray but are positioned above the supply tray.
In still another aspect of the invention, there is provided a color image forming device including the frame, the elongated intermediate image transfer member, the plurality of electrostatic latent image bearing bodies, the plurality of developing units each includes the developing agent bearing body, a secondary image transfer device, a fixing device, and a reverse mechanism. The secondary image transfer device is positioned immediately below the intermediate image transfer member for transferring an image from the intermediate image transfer member onto an image recording medium. The fixing device is adapted for fixing the image onto the image recording medium after the image has been transferred from the intermediate image transfer member onto the image recording medium. The reverse mechanism is adapted for reversing a surface of the image recording medium to provide another image onto a reverse surface of the identical image recording medium. The reverse mechanism is connected to a downstream of the fixing device and to an upstream of the secondary image transfer device by way of a reverse print pathway extending below the intermediate image transfer member.